Short-range wireless communication technologies are well-known for use in wireless personal area networks (WPANs). Such technologies include, but are not limited to, Bluetooth®, wireless Universal Serial Bus (Wireless USB), Wi-Fi®, Z-Wave®, ZigBee®, and IrDA®. Of these technologies, the use of Bluetooth technology is most prevalent for WPANs involving short-range communications between wireless accessory devices and wireless wide area network (WWAN) devices, such as cellular phones, smartphones, laptop computers, tablet computers, and personal digital assistants (PDAs).
As discussed in detail in U.S. Patent Application Publication No. US 2006/0072525 A1, Bluetooth wireless technology is an international, open standard for allowing intelligent devices to communicate with each other through wireless, short-range communications. Bluetooth technology allows any Bluetooth-enabled device, such as a computer, smartphone, keyboard, printer, or hands-free device (e.g., a headset or earpiece), to make its own wireless connections to other Bluetooth-enabled devices without any direct action from a user.
Bluetooth wireless technology enables multiple simultaneous connections between Bluetooth-enabled devices. For example, a Bluetooth-enabled computer (e.g., a personal computer, laptop computer, or tablet computer) may be connected to a Bluetooth printer and a Bluetooth mouse. As another example, a Bluetooth-enabled palmtop computer with MP3 functionality, such as an iPod Touch® device, may be connected to a Bluetooth headset and a Bluetooth speaker. Additionally, certain Bluetooth devices, such as audio gateways, facilitate connection of other Bluetooth devices to devices that are not Bluetooth-enabled. For example, a Bluetooth audio gateway may be used to connect a Bluetooth-enabled cellular phone to a cordless telephone base station to allow incoming cellular phone calls to be answered using a home's cordless telephones. Alternatively, a Bluetooth audio gateway may be embedded into cellular or smartphone to facilitate communications between a Bluetooth headset and a cellular network.
When two or more complex Bluetooth-enabled devices wirelessly connect together, they form a network that is typically referred to as a “piconet.” Each device in a Bluetooth piconet may be characterized by a role, such as a master role or a slave role, with respect to the audio and/or data connections in the piconet. According to the Bluetooth specification, there may be one piconet master device and up to seven piconet slave devices. Additionally according to the Bluetooth specification, a device that initiates a Bluetooth connection is deemed to be the default master device and a device that accepts a connection is deemed to be a default slave device.
Bluetooth devices may operate in more than one piconet and, therefore, may simultaneously perform one or more roles with respect to the audio and/or data connections in the various piconets. For example, a Bluetooth device may operate as a master in a first piconet and as a slave in a second piconet, as a slave in both piconets, or as a master in both piconets, depending on how the Bluetooth connections originated in the piconets. A Bluetooth device's simultaneous participation as a master or slave in one piconet and a slave in another piconet is typically referred to as involvement in a “scatternet.” Scatternet operation is supported by some, but not all, Bluetooth chipsets, and some Bluetooth chipsets have better scatternet support than others. In this regard, some Bluetooth chipsets are adapted to support master and slave operating modes, but others are adapted to support only master or only slave operating modes.
During operation of connected Bluetooth devices, one or more roles of the devices may be switched if the Bluetooth devices support role switching. For example, one or more roles may be switched upon connection of an additional Bluetooth device to an existing piconet of Bluetooth devices. Role switching is often necessary and may even be required in certain circumstances. For example, a Bluetooth network access point may require all peer devices to be slaves and initiate a role switch whenever a connection is attempted. However, not all Bluetooth devices support role switching and either unsupported role switching or improperly managed role switching may cause an unsupported scatternet scenario. Such a scenario may result in rejection of a new Bluetooth connection request and/or abnormal dropping of one or more existing Bluetooth links due to unsupported role profiles and/or unauthorized role switching requests within a conventional piconet of Bluetooth devices. The likelihood of abnormal link dropping or loss typically increases in situations where a Bluetooth device with unsupported or poorly managed role switching is connected in a slave role to one Bluetooth audio gateway and then attempts to simultaneously connect to another Bluetooth audio gateway in a default master role. The increased risk of link loss is generally due to the link management requirements imposed upon the device when acting in the role of slave interfering with the audio transmission requirements of the device when acting as a master.
Managing of device roles and role switching may help reduce the likelihood of creating an unsupported scatternet scenario. One technique for managing the switching of roles between Bluetooth devices is described in U.S. Patent Application Publication No. US 2006/0072525 A1, which is incorporated herein by this reference. According to the technique disclosed in the publication, a Bluetooth device that supports role switching and receives a new connection request determines whether to switch from a current role (which would be a slave role by default) to another role (e.g., master) based on a stored role management table. The role management table may include desired roles based on the type of application as specified by a particular Bluetooth profile (e.g., advanced audio distribution profile (A2DP), general access profile (GAP), generic audio/visual distribution profile (GAVDP), and so forth).
However, even in scenarios where role switching is well managed, abnormal link loss may still occur. For example, according to the Bluetooth specification, a Bluetooth audio gateway (e.g., in a cellular phone or smartphone) can request to become a piconet master and a Bluetooth accessory (e.g., a hands-free device) is obligated to accept the request, resulting in the accessory becoming a slave. The accessory can then subsequently request to become a master due to establishing another Bluetooth connection, but not all audio gateways (e.g., those in certain cellular phones and smartphones) permit role switching to a slave role. Therefore, where the accessory's request to role switch is refused, the accessory remains in the slave role, which results in a scatternet scenario and an increased risk for abnormal link loss if the accessory attempts to connect to another audio gateway (e.g., in another cellular phone or smartphone).
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated alone or relative to other elements to help improve the understanding of the various embodiments of the present invention.